/*
 * %W% %E%
 *
 * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package javax.security.auth.kerberos;

import java.util.*;
import java.security.Permission;
import java.security.PermissionCollection;
import java.io.ObjectStreamField;
import java.io.ObjectOutputStream;
import java.io.ObjectInputStream;
import java.io.IOException;

/**
 * This class is used to protect Kerberos services and the 
 * credentials necessary to access those services. There is a one to 
 * one mapping of a service principal and the credentials necessary
 * to access the service. Therefore granting access to a service
 * principal implicitly grants access to the credential necessary to
 * establish a security context with the service principal. This
 * applies regardless of whether the credentials are in a cache
 * or acquired via an exchange with the KDC. The credential can
 * be either a ticket granting ticket, a service ticket or a secret
 * key from a key table.
 * <p>
 * A ServicePermission contains a service principal name and
 * a list of actions which specify the context the credential can be
 * used within.
 * <p>
 * The service principal name is the canonical name of the
 * <code>KereberosPrincipal</code> supplying the service, that is
 * the KerberosPrincipal represents a Kerberos service
 * principal. This name is treated in a case sensitive manner.
 * An asterisk may appear by itself, to signify any service principal.
 * <p>
 * Granting this permission implies that the caller can use a cached
 * credential (TGT, service ticket or secret key) within the context
 * designated by the action. In the case of the TGT, granting this
 * permission also implies that the TGT can be obtained by an
 * Authentication Service exchange.
 * <p>
 * The possible actions are:
 * <p>
 * <pre>
 *    initiate -              allow the caller to use the credential to
 *                            initiate a security context with a service
 *                            principal.
 *
 *    accept -                allow the caller to use the credential to
 *                            accept security context as a particular
 *                            principal.
 * </pre>
 *
 * For example, to specify the permission to access to the TGT to
 * initiate a security context the permission is constructed as follows:
 * <p>
 * <pre>
 *     ServicePermission("krbtgt/EXAMPLE.COM@EXAMPLE.COM", "initiate");
 * </pre>
 * <p>
 * To obtain a service ticket to initiate a context with the "host"
 * service the permission is constructed as follows:
 * <pre>
 *     ServicePermission("host/foo.example.com@EXAMPLE.COM", "initiate");
 * </pre>
 * <p>
 * For a Kerberized server the action is "accept". For example, the permission
 * necessary to access and use the secret key of the  Kerberized "host"
 * service (telnet and the likes)  would be constructed as follows:
 * <p>
 * <pre>
 *     ServicePermission("host/foo.example.com@EXAMPLE.COM", "accept");
 * </pre>
 * 
 * @since 1.4
 */

public final class ServicePermission extends Permission
    implements java.io.Serializable {

    private static final long serialVersionUID = -1227585031618624935L;

    /**
     * Initiate a security context to the specified service
     */
    private final static int INITIATE	= 0x1;

    /**
     * Accept a security context
     */
    private final static int ACCEPT	= 0x2;

    /**
     * All actions
     */ 
    private final static int ALL	= INITIATE|ACCEPT;

    /**
     * No actions.
     */
    private final static int NONE    = 0x0;

    // the actions mask
    private transient int mask;

    /**
     * the actions string. 
     *
     * @serial
     */

    private String actions; // Left null as long as possible, then
                            // created and re-used in the getAction function.

    /**
     * Create a new <code>ServicePermission</code>
     * with the specified <code>servicePrincipal</code>
     * and <code>action</code>.
     *
     * @param servicePrincipal the name of the service principal.
     * An asterisk may appear by itself, to signify any service principal.
     * <p>
     * @param action the action string
     */
    public ServicePermission(String servicePrincipal, String action) {
	super(servicePrincipal);
	init(servicePrincipal, getMask(action));
    }


    /**
     * Initialize the ServicePermission object.
     */
    private void init(String servicePrincipal, int mask) {

	if (servicePrincipal == null) 
		throw new NullPointerException("service principal can't be null");

	if ((mask & ALL) != mask) 
	    throw new IllegalArgumentException("invalid actions mask");

	this.mask = mask;
    }


    /**
     * Checks if this Kerberos service permission object "implies" the 
     * specified permission.
     * <P>
     * If none of the above are true, <code>implies</code> returns false.
     * @param p the permission to check against.
     *
     * @return true if the specified permission is implied by this object,
     * false if not.  
     */
    public boolean implies(Permission p) {
	if (!(p instanceof ServicePermission))
	    return false;

	ServicePermission that = (ServicePermission) p;

	return ((this.mask & that.mask) == that.mask) &&
	    impliesIgnoreMask(that);
    }
    
    
    boolean impliesIgnoreMask(ServicePermission p) {
	return ((this.getName().equals("*")) ||
		this.getName().equals(p.getName()));
    }

    /**
     * Checks two ServicePermission objects for equality. 
     * <P>
     * @param obj the object to test for equality with this object.
     * 
     * @return true if <i>obj</i> is a ServicePermission, and has the
     *  same service principal, and actions as this
     * ServicePermission object.
     */
    public boolean equals(Object obj) {
	if (obj == this)
	    return true;

	if (! (obj instanceof ServicePermission))
	    return false;

	ServicePermission that = (ServicePermission) obj;
	return ((this.mask & that.mask) == that.mask) && 
	    this.getName().equals(that.getName());
		

    }

    /**
     * Returns the hash code value for this object.
     *
     * @return a hash code value for this object.
     */

    public int hashCode() {
	return (getName().hashCode() ^ mask);
    }
    

    /**
     * Returns the "canonical string representation" of the actions in the
     * specified mask.
     * Always returns present actions in the following order: 
     * initiate, accept.
     *
     * @param mask a specific integer action mask to translate into a string
     * @return the canonical string representation of the actions
     */
    private static String getActions(int mask)
    {
	StringBuilder sb = new StringBuilder();
        boolean comma = false;

	if ((mask & INITIATE) == INITIATE) {
	    if (comma) sb.append(',');
    	    else comma = true;
	    sb.append("initiate");
	}

	if ((mask & ACCEPT) == ACCEPT) {
	    if (comma) sb.append(',');
    	    else comma = true;
	    sb.append("accept");
	}

	return sb.toString();
    }

    /**
     * Returns the canonical string representation of the actions.
     * Always returns present actions in the following order:
     * initiate, accept.
     */
    
    public String getActions() {
	if (actions == null)
	    actions = getActions(this.mask);

	return actions;
    }

    
    /**
     * Returns a PermissionCollection object for storing
     * ServicePermission objects.
     * <br>
     * ServicePermission objects must be stored in a manner that
     * allows them to be inserted into the collection in any order, but
     * that also enables the PermissionCollection implies method to
     * be implemented in an efficient (and consistent) manner.
     *
     * @return a new PermissionCollection object suitable for storing
     * ServicePermissions.
     */

    public PermissionCollection newPermissionCollection() {
	return new KrbServicePermissionCollection();
    }

    /**
     * Return the current action mask.
     *
     * @return the actions mask.
     */

    int getMask() {
	return mask;
    }

    /**
     * Convert an action string to an integer actions mask. 
     *
     * @param action the action string
     * @return the action mask
     */

    private static int getMask(String action) {

	if (action == null) {
	    throw new NullPointerException("action can't be null");
	}

	if (action.equals("")) {
	    throw new IllegalArgumentException("action can't be empty");
	}

	int mask = NONE;

	char[] a = action.toCharArray();

	int i = a.length - 1;
	if (i < 0)
	    return mask;

	while (i != -1) {
	    char c;

	    // skip whitespace
	    while ((i!=-1) && ((c = a[i]) == ' ' ||
			       c == '\r' ||
			       c == '\n' ||
			       c == '\f' ||
			       c == '\t'))
		i--;

	    // check for the known strings
	    int matchlen;

	    if (i >= 7 && (a[i-7] == 'i' || a[i-7] == 'I') &&
			  (a[i-6] == 'n' || a[i-6] == 'N') &&
			  (a[i-5] == 'i' || a[i-5] == 'I') &&
			  (a[i-4] == 't' || a[i-4] == 'T') &&
			  (a[i-3] == 'i' || a[i-3] == 'I') &&
			  (a[i-2] == 'a' || a[i-2] == 'A') &&
			  (a[i-1] == 't' || a[i-1] == 'T') &&
			  (a[i] == 'e' || a[i] == 'E'))
	    {
		matchlen = 8;
		mask |= INITIATE;

	    } else if (i >= 5 && (a[i-5] == 'a' || a[i-5] == 'A') &&
				 (a[i-4] == 'c' || a[i-4] == 'C') &&
				 (a[i-3] == 'c' || a[i-3] == 'C') &&
				 (a[i-2] == 'e' || a[i-2] == 'E') &&
				 (a[i-1] == 'p' || a[i-1] == 'P') &&
				 (a[i] == 't' || a[i] == 'T'))
	    {
		matchlen = 6;
		mask |= ACCEPT;

	    } else {
		// parse error
		throw new IllegalArgumentException(
			"invalid permission: " + action);
	    }

	    // make sure we didn't just match the tail of a word
	    // like "ackbarfaccept".  Also, skip to the comma.
	    boolean seencomma = false;
	    while (i >= matchlen && !seencomma) {
		switch(a[i-matchlen]) {
		case ',':
		    seencomma = true;
		    /*FALLTHROUGH*/
		case ' ': case '\r': case '\n':
		case '\f': case '\t':
		    break;
		default:
		    throw new IllegalArgumentException(
			    "invalid permission: " + action);
		}
		i--;
	    }

	    // point i at the location of the comma minus one (or -1).
	    i -= matchlen;
	}

	return mask;
    }


    /**
     * WriteObject is called to save the state of the ServicePermission 
     * to a stream. The actions are serialized, and the superclass
     * takes care of the name.
     */
    private void writeObject(java.io.ObjectOutputStream s)
        throws IOException
    {
	// Write out the actions. The superclass takes care of the name
	// call getActions to make sure actions field is initialized
	if (actions == null)
	    getActions();
	s.defaultWriteObject();
    }

    /**
     * readObject is called to restore the state of the
     * ServicePermission from a stream.
     */
    private void readObject(java.io.ObjectInputStream s)
         throws IOException, ClassNotFoundException
    {
	// Read in the action, then initialize the rest
	s.defaultReadObject();
	init(getName(),getMask(actions));
    }


    /*
      public static void main(String args[]) throws Exception {
      ServicePermission this_ =
      new ServicePermission(args[0], "accept");
      ServicePermission that_ =
      new ServicePermission(args[1], "accept,initiate");
      System.out.println("-----\n");
      System.out.println("this.implies(that) = " + this_.implies(that_));
      System.out.println("-----\n");
      System.out.println("this = "+this_);
      System.out.println("-----\n");
      System.out.println("that = "+that_);
      System.out.println("-----\n");

      KrbServicePermissionCollection nps =
      new KrbServicePermissionCollection();
      nps.add(this_);
      nps.add(new ServicePermission("nfs/example.com@EXAMPLE.COM",
      "accept"));
      nps.add(new ServicePermission("host/example.com@EXAMPLE.COM",
      "initiate"));
      System.out.println("nps.implies(that) = " + nps.implies(that_));
      System.out.println("-----\n");

      Enumeration e = nps.elements();
	
      while (e.hasMoreElements()) {
      ServicePermission x =
      (ServicePermission) e.nextElement();
      System.out.println("nps.e = " + x);
      }

      }
    */
    
}


final class KrbServicePermissionCollection extends PermissionCollection 
    implements java.io.Serializable {

    // Not serialized; see serialization section at end of class
    private transient List perms;

    public KrbServicePermissionCollection() {
	perms = new ArrayList();
    }
    
    /**
     * Check and see if this collection of permissions implies the permissions 
     * expressed in "permission".
     *
     * @param p the Permission object to compare
     *
     * @return true if "permission" is a proper subset of a permission in 
     * the collection, false if not.
     */

    public boolean implies(Permission permission) {
	if (! (permission instanceof ServicePermission))
   		return false;

	ServicePermission np = (ServicePermission) permission;
	int desired = np.getMask();
	int effective = 0;
	int needed = desired;

	synchronized (this) {
	    int len = perms.size();
	
	    // need to deal with the case where the needed permission has
	    // more than one action and the collection has individual permissions
	    // that sum up to the needed.

	    for (int i = 0; i < len; i++) {
		ServicePermission x = (ServicePermission) perms.get(i);

		//System.out.println("  trying "+x);
		if (((needed & x.getMask()) != 0) && x.impliesIgnoreMask(np)) {
		    effective |=  x.getMask();
		    if ((effective & desired) == desired)
			return true;
		    needed = (desired ^ effective);
		}
	    }
	}
	return false;
    }

    /**
     * Adds a permission to the ServicePermissions. The key for
     * the hash is the name.
     *
     * @param permission the Permission object to add.
     *
     * @exception IllegalArgumentException - if the permission is not a
     *                                       ServicePermission
     *
     * @exception SecurityException - if this PermissionCollection object
     *                                has been marked readonly
     */

    public void add(Permission permission) {
	if (! (permission instanceof ServicePermission))
	    throw new IllegalArgumentException("invalid permission: "+
					       permission);
	if (isReadOnly())
	    throw new SecurityException("attempt to add a Permission to a readonly PermissionCollection");

	synchronized (this) {
	    perms.add(0, permission);
	}
    }

    /**
     * Returns an enumeration of all the ServicePermission objects
     * in the container.
     *
     * @return an enumeration of all the ServicePermission objects.
     */

    public Enumeration elements() {
        // Convert Iterator into Enumeration
	synchronized (this) {
	    return Collections.enumeration(perms);
	}
    }

    private static final long serialVersionUID = -4118834211490102011L;

    // Need to maintain serialization interoperability with earlier releases,
    // which had the serializable field:
    // private Vector permissions;

    /**
     * @serialField permissions java.util.Vector
     *     A list of ServicePermission objects.
     */
    private static final ObjectStreamField[] serialPersistentFields = {
        new ObjectStreamField("permissions", Vector.class),
    };

    /**
     * @serialData "permissions" field (a Vector containing the ServicePermissions).
     */
    /*
     * Writes the contents of the perms field out as a Vector for
     * serialization compatibility with earlier releases.
     */
    private void writeObject(ObjectOutputStream out) throws IOException {
	// Don't call out.defaultWriteObject()

	// Write out Vector
	Vector permissions = new Vector(perms.size());

	synchronized (this) {
	    permissions.addAll(perms);
	}

        ObjectOutputStream.PutField pfields = out.putFields();
        pfields.put("permissions", permissions);
        out.writeFields();
    }

    /*
     * Reads in a Vector of ServicePermissions and saves them in the perms field.
     */
    private void readObject(ObjectInputStream in) throws IOException, 
    ClassNotFoundException {
	// Don't call defaultReadObject()

	// Read in serialized fields
	ObjectInputStream.GetField gfields = in.readFields();

	// Get the one we want
	Vector permissions = (Vector)gfields.get("permissions", null);
	perms = new ArrayList(permissions.size());
	perms.addAll(permissions);
    }
}
